Field
The present disclosure relates to a voltage converter system.
Related Art
A voltage converter system configured to convert an input voltage into a target voltage may be used, for example, in a fuel cell system to convert an output voltage of a fuel cell into a target voltage. The voltage converter system has a voltage conversion circuit including a reactor configured to serve as an inductance element and a switching element configured to control the magnitude of electric current flowing through the reactor (hereinafter called “reactor current”). The voltage converter system adjusts the duty ratio of opening and closing the switching element, so as to control the value of output voltage. In a voltage converter system equipped with a plurality of voltage conversion circuits, an inductance component of each reactor may be deviated from its designed value, due to the manufacturing error of each individual, a temperature change, aging and the like. In this case, even when the switching element is opened and closed at a duty ratio corresponding to a target value of reactor current, the flow of electric current is deviated from the target value of reactor current. This results in failing to output a target voltage. One configuration of the voltage converter system has accordingly been proposed to measure the value of reactor current flowing through each reactor and adjust the duty ratio based on the measured current value (as described in JP 2015-19448A).
In one possible configuration, one current sensor is provided for each reactor (each voltage conversion circuit), in order to measure the value of reactor current flowing through each reactor. This configuration enables the value of each reactor current to be accurately detected but increases the total number of current sensors. This causes problems, for example, expansion in size of the voltage converter system and an increase in manufacturing cost. One configuration of the voltage converter system has accordingly been proposed to provide one current sensor to be shared by two adjoining reactors (as described in JP 4410693B).
In the voltage converter system described in JP 4410693B, however, the current sensor is configured to measure only a difference value between values of electric current flowing through the two adjoining reactors. This configuration fails to accurately detect the values of electric current flowing through the respective reactors. This results in failing to accurately adjust the duty ratios of the respective switching elements, based on the values of electric current flowing through the respective reactors. With regard to a voltage converter system equipped with a plurality of voltage conversion circuits, there is accordingly a demand for a technique that allows for accurate adjustment of the duty ratio in each of the voltage conversion circuits, while suppressing expansion in size of the voltage converter system and an increase in cost.